Bug 464237

Summary:	thumbnail generation not working right
Product:	[Frameworks and Libraries] kio-extras	Reporter:	Michael <michael.hmich>
Component:	Thumbnails and previews	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	REPORTED ---
Severity:	normal	CC:	nicolas.fella
Priority:	NOR
Version First Reported In:	22.12.1
Target Milestone:	---
Platform:	Neon
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	thumb cache cleaning

Description Michael 2023-01-13 13:50:00 UTC

Created attachment 155258 [details]
thumb cache cleaning

since I find some discrepancies with thumbnail generation ( https://bugs.kde.org/show_bug.cgi?id=464046 ) I started to look closer

the thumbnail cache in ~/cache/thumbnails/ seems never being maintained or cleaned
what leads to the problem that thousands of thumbs might get stored (attachment)

thumb generation always was kind of slow, one of the reasons likely is the number of thumbs already in cache
specially slow it was and now it still is worse with camera raw images

times ago, because of this slowdown, I limited my camera files count to 200/directory, it is quite normal for a photographer having an average of 300+ files per day 

thumbs are stored as PNGs, I believe that storing as JPGs would be really faster, I tried it with a third party thumb generator and 128px wide thumbs, in a directory with 200 camera JPGs, using the JPG format for thumbs finished in half of the time needed for PNGs

may be you consider it and check if you can change to jpg thumbs

in any case I would like to have a configurable option how many days I want to hold my thumbs, being deleted after automatically

then I think that the thumbnail cache would be better placed in the image directory as .thumbs or something, I access the same places from different machines, this would eliminate a lot of local home/.cache storage space and much faster processing in the end

Comment 1 Nicolas Fella 2023-01-14 12:58:12 UTC

The XDG thumbnail specification specifies the format to be PNG (https://specifications.freedesktop.org/thumbnail-spec/thumbnail-spec-latest.html#CREATION), so this isn't going to change

Comment 2 Michael 2023-01-14 22:04:00 UTC

(In reply to Nicolas Fella from comment #1)
> The XDG thumbnail specification specifies the format to be PNG
> (https://specifications.freedesktop.org/thumbnail-spec/thumbnail-spec-latest.
> html#CREATION), so this isn't going to change

I see, don't know the reason but maybe not so important right now
the removing thumbs part of the doc is very thin and probably not implemented anywhere, some other parts could also need some reading and modification 

meanwhile, I moved and merged all my thumb caches to the image work dir on the server and symlinked it for now on all machines, and that gave a real better performance in comparison to how it was, the thumbs are also compatible between the different OSs, even FreeBSD, so far that is for me, but hard to suggest it as solution to average users

certainly, the doc and its contributors never previewed that people might have a very large number of image files, means that the actual thumb generation process is too slow  for handling it

I hope that the "cleaning after N days" isn't so difficult to add and that it is there some day 

thanks for the link

Comment 3 Michael 2023-01-19 18:59:33 UTC

does this help?

this days was there an update and kio was part, upgrade to
Package: kio
Version: 5.102.0-0xneon+22.04+jammy+release+build22

since then dolphin did not display anymore the raw files

after removing kio no image thumb/preview was displayed anymore while gwenview kept working normally

shows dolphin depends on kio and gwenview not

so why is that and why dolphin can not treat thumbs like gwenview does?

Comment 4 Michael 2023-01-19 22:22:55 UTC

but then I wonder why Arch keeps working fine

local/dolphin 22.12.1-1 (kde-applications kde-system)
local/dolphin-plugins 22.12.1-1 (kde-applications kdesdk)
local/gwenview 22.12.1-1 (kde-applications kde-graphics)
local/kio 5.101.0-2 (kf5)
local/kio-extras 22.12.1-1 (kde-applications kde-network)